#define  _CRT_SECURE_NO_WARNINGS  1
#include <stdio.h>
#include <string.h>
int main()
{
	char arr[1001] = { 0 };
	char t;
	while ((scanf("%s", arr)) != EOF)
	{
		int len = strlen(arr);
		int i = 0;
		for (i = 0; i < len; i++)
		{
			int j = 0;
			char min = arr[i];
			for (j = i; j < len; j++)
			{
				if (arr[j] < min)
				{
					t = min;
					min = arr[j];
					arr[j] = t;
				}
			}
			printf("%c", min);
		}
		printf("\n");
	}


	return 0;
}